Evaluating North American Tallgrass Prairie Quality Using The Auchenorrhyncha Quality Index
Auchenorrhyncha (i.e., leafhoppers, treehoppers, spittlebugs, and planthoppers) represent some most diverse groups of herbivorous insects in the tallgrass prairie, they have close associations with many native prairie grasses and forbs, and respond in predictable ways to changes in grassland degradation. These attributes make Auchenorrhyncha ideal candidates in the development of a habitat quality index to measure tallgrass prairie integrity. Chapter 1 provides a detailed introduction of ecological integrity, methods used in measuring tallgrass prairie integrity, and the usefulness of insects in assessing prairie integrity. Chapter 2 describes the development of the Auchenorrhyncha Quality Index (AQI), and examines how changes in robustness (vacuum and sweeping) and sensitivity (changes in time of year and prairie community) affected two versions of the AQI (with abundance [AQIw/N] and without abundance [AQIw/outN]). The AQI was computed by assigning each auchenorrhynchan species a Coefficient of Conservatism (CC) value, which ranged from 0 (habitat-generalist/tolerant to degradation) to 18 (prairie-dependent/intolerant to degradation). These CC values are averaged and combined with species richness producing the AQIw/outN or these values are summed and weighted with abundance and combined with species richness producing the AQIw/N. The robustness and sensitivity of both versions of the AQI were analyzed by collecting Auchenorrhyncha from 35 sites in 4 states (Illinois, Wisconsin, Iowa, and Missouri) over 3 years (2004, 2005, and 2008) using a combination of sweeping and/or vacuuming from transects and/or 5x5m plots from wet-mesic, loess, glacial-drift, gravel hill prairies, and sand prairies. ANOVAs showed that both versions of the AQI were insensitive to changes in time of year and prairie community at the landscape level when sampling from four transects using a vacuum but both versions of the AQI exhibited variation on individual sites when vacuum or sweep sampling throughout the growing season and on wet prairies. Chapter 3 examined the ability of the AQI and related measures of Auchenorryncha integrity, and vegetation-based measures of integrity and diversity in discriminating glacial-drift hill prairie quality on 14 sites in Illinois; and examined the relationships between Auchenorrhyncha integrity and diversity and vegetation integrity and diversity. Both Auchenorrhyncha and vegetation integrity discriminated quality in similar ways and prairie Auchenorrhyncha diversity was positively associated with native prairie grasses. Chapter 4 examined the effects of prescribed burning on the AQI and related measures of Auchenorrhyncha integrity and diversity on 22 loess hill prairies in Illinois. These results showed that recently burned and frequently burned sites exhibited lower Auchenorrhnyncha integrity and diversity values than unburned prairies.
Auchenorrhyncha, Habitat Quality Index, Tallgrass Prairie
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign